In this paper is gived one interesting method for proving algebraic inequalities. This method for the case of algebraic inequality for three variables $f(x,y,z)geq0$; $(x,y,z>0)$ $f(x,y,z)geq0$; $(x,y,z>0)$ \[ f(x,y,z)\geq f(t,t,z), \] where is for example $t=\frac{x+y}2$. Then we prove that holds the inequality \[ f(t,t,z)\geq0. \]